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J(j 8828 



Bureau of Mines Information Circular/1980 



Surface Mine Truck Safety 

Proceedings: Bureau of Mines Technology Transfer 
Seminars, Minneapolis, Minn., June 25, 1980, 
Birmingham, Ala. , July 9, 1980, 
and Tucson, Ariz., July 24, 1980 



Compiled by Staff— Bureau of Mines 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 8828 

Surface Mine Truck Safety 

Proceedings: Bureau of Mines Technology Transfer 
Seminars, Minneapolis, Minn., June 25, 1980, 
Birmingham, Ala. , July 9, 1980, 
and Tucson, Ariz., July 24, 1980 

Compiled by Staff— Bureau of Mines 




UNITED STATES DEPARTMENT OF THE INTERIOR 
Cecil D. Andrus, Secretary 

BUREAU OF MINES 

Lindsay D. Norman, Acting Director 



% 






', /r 



This publication has been cataloged as follows: 



Bureau of Mines Technology Transfer Seminars, Minneapolis, 
Minn., Birmingham, Ala., and Tucson, Ariz., 1980 

Surface mine truck safety. Proceedings: Bureau of Mines 
Technology Transfer Seminars, Minneapolis, Minn., June 25, 
1980, Birmingham, Ala., July 9, 1980, and Tucson, Ariz., July 24, 
1980. 

(Information circular - Bureau of Mines ; 8828) 

Includes bibliographies. 

Supt. of Docs, no.: I 28.27:8828 

1. Strip mining— Safety measures— Congresses. I. United States. 
Bureau of Mines. II. Series: United States. Bureau of Mines. Infor- 
mation circular ; 8828. 

TN295.U4 [TN291] 622s [622'.8] 80-607905 



PREFACE 

This Information Circular summarizes recent Bureau of Mines research 
results concerning improved haulage truck safety in our country's surface 
mines. The papers are only a sample of the Bureau's total effort to improve 
large mobile mine equipment safety, but they delineate the major concerns of 
the program. Much of the technology discussed is applicable to other types 
of mining equipment. 

The four technical presentations reproduced herein were made by Bureau 
personnel at the Technology Transfer Seminars on Surface Mine Truck Safety 
given in June and July 1980 in Minneapolis, Minn., Birmingham, Ala., and 
Tucson, Ariz. Those desiring more information on the Bureau's surface mine 
safety program in general, or information on specific situations, should feel 
free to contact the Bureau of Mines Division of Minerals Health and Safety 
Technology, 2401 E Street, N.W. , Washington, D.C., 20241, or the appropriate 
author. 



CONTENTS 

Page 

Preface i 

Abstract 1 

Introduction, by W. Thomas Cocke 2 

Protecting haulage trucks from fire, by William H. Pomroy 4 

Improved visibility systems , by Guy A. Johnson 22 

Improved ingress/egress systems for large haulage trucks: development 

and in-mine testing, by David A. Johnson 40 

Training mobile equipment operators, by Louis Schaffer and Edwin Ayres . . 52 



SURFACE MINE TRUCK SAFETY 

Proceedings: Bureau of Mines Technology Transfer Seminars, Minneapolis, Minn., 
June 25, 1980, Birmingham, Ala., July 9, 1980, and Tucson, Ariz., July 24, 1980 

Compiled by Staff-Bureau of Mines 



ABSTRACT 

These proceedings consist of an introduction and four descriptive papers. 
The first paper is an update on fire protection for large haulage vehicles, 
the second paper is concerned with improved visibility systems for large haul- 
age vehicles, the third paper is on improved ladders for large haulage vehicles, 
and the fourth paper is concerned with large haulage vehicle operator training 
systems. 



INTRODUCTION 

by 

W. Thomas Cocke 1 



Maintaining safety in large mine haulage vehicles becomes more complex as 
this equipment becomes larger in order to increase productivity. Due to these 
changes in equipment size, an increasing number of surface mine accidents has 
resulted. The problems relating to size are (1) safety during fire emergen- 
cies, (2) slip and fall accidents, (3) reduced visibility, and (4) inadequate 
operator training. 

Fires in particular are a serious hazard to equipment and personnel. 
Not only has property damage become excessive as trucks become larger, but 
increased danger to personnel also has resulted. The operator's inability to 
detect fire and escape due to increased cab height, the cab's position on the 
vehicle, and location of the ladder are common causes of serious personal 
injuries. 

Slip and fall accidents have become the major cause of lost time injuries 
associated with large haulage vehicles. These are caused by hazards intro- 
duced in the design of truck ladders and by inadequate maintenance. 

Visibility, too, is a major mine safety problem in large mobile mine 
equipment because of reduced operator field-of-view due to the operator's 
position on the vehicle and the increased amount of adjacent equipment. Visi- 
bility is the cause of an increasing number of surface mine accidents. 

Accident and training research has shown that one of the principal rea- 
sons for the number of accidents in surface mines is inadequate training of 
mobile equipment operators. This is especially evident in operator inability 
to cope with emergency situations. 

The objective of the Bureau's research programs is to develop new and 
improved technology and equipment to protect miners against these hazards. 
Through a program of contract and in-house research, the Bureau has developed 
and in-mine demonstrated reasonably priced, reliable fire protection equipment; 
evaluated safety hazards associated with routine use of ladders and emergency 
egress, developed improved ladder designs, and conducted in-mine tests; devel- 
oped and tested an improved visibility system of mirrors and closed-circuit 
television; and formulated a concept for providing needed training of mobile 
equipment operators. 



!Staff engineer, Division of Minerals Health and Safety Technology, Bureau of 
Mines, Washington, D.C. 



The Bureau is conducting other research relating to large haulage vehi- 
cles. Anticollision research involving close proximity warning and driver 
alertness devices is another approach to problems relating to safety in these 
vehicles. Novel cab designs are also being investigated. Future research may 
delve into complete automation. 

Development of standards is not an overriding objective of the Bureau of 
Mines. The Bureau is striving instead to develop improved mine safety tech- 
nology that is sufficiently cost-effective so that acceptance and use by the 
mining industry will occur voluntarily. Research results, in order to be 
useful, must be transferred to the mining industry, equipment manufacturers, 
and other involved parties. Technology transfer is a major program of the 
Bureau, one aspect of which is seminars. The papers presented here address 
the problems outlined above and other related problems. 



PROTECTING HAULAGE TRUCKS FROM FIRE 
by 
William H. Pomroy 1 



ABSTRACT 

Fires on surface mine haulage trucks are a serious hazard to life and 
property. The Bureau of Mines, through a program of contract and in-house 
research, has developed and in-mine demonstrated reasonably priced, reliable 
automatic fire protection systems to deal with this problem. This report 
describes the development and subsequent in-mine tests of these systems. 

A variety of fire sensors, extinguishing agents, and control systems are 
discussed in the context of mine equipment designs and operating environments. 

INTRODUCTION 

Fires on large surface mine haulage trucks are a serious hazard to life 
and property. The size of these machines magnifies the problem by increasing 
the potential for fires, obstructing the operator's view of fire hazards, and 
restricting the operator's egress from the vehicle. Serious personal injuries 
frequently result, and property damages in excess of $100,000 per fire are not 
uncommon (fig. 1). In addition, mines suffer lost production while waiting 
for damaged equipment to be repaired or for new equipment to be delivered. 

Acknowledging this problem, regulatory agencies and insurance companies 
require the installation of fire protection hardware on this equipment. Usu- 
ally a hand-portable extinguisher is mounted in or near the operator's cab, 
with perhaps another mounted elsewhere on the vehicle. With the increasing 
size of vehicles, however, hand-portables no longer can provide adequate pro- 
tection, so many manufacturers have begun to offer manually activated, fixed 
fire suppression systems to supplement the use of hand-portables. 

Manually activated fixed fire suppression systems consist of one or more 
fire suppressent containers connected by a fixed plumbing network to nozzles 
directed at specific, predetermined fire hazard areas (fig. 2). To use the 
system, the operator must detect the fire and activate a cab-mounted electric 
or pneumatic releasing device. The large size of this equipment, however, 
makes it difficult for an operator to see the fire until it has grown out of 
control. Operators often panic, fail to activate the system, and in their 
haste to escape the fire, jump from the cab to the ground, sustaining serious 
injury. 



iMining engineer, Twin Cities Research Center, Bureau of Mines, Twin Cities, 
Minn. 




FIGURE 1. - Typical fire on mine haulage truck. 



Manual actuator 



Instruction 
nameplate 

Dry chemical 
discharge nozzle 



Manual actuator 



Instruction 
nameplate 




Dry chemical container 



FIGURE 2. - Manually operated fixed fire protection system for haulage truck. 



To correct the problems inherent with manually activated systems, the 
Bureau of Mines developed automatic fire sensing and suppression systems for 
mining equipment. This program sought to demonstrate, through in-mine hardware 
tests, that fire protection technology existed from which rugged, reliable, 
cost-effective automatic systems for mine equipment could be developed. 
Wherever possible, off-the-shelf components were to be used. Numerous combi- 
nations of components were tested to demonstrate the flexibility of available 
design options. Haulage trucks were selected for the initial development 
program, because their fire hazards are typical of those found on most types 
of mine equipment and because they comprise the largest class of mine vehicles. 

FIRST-GENERATION SYSTEM DESIGNS 

Typical fire hazard areas on mine haulage vehicles include the engine, 
transmission, fuel tanks, and in some cases, dynamic brake grids. Parking 
brake and dashboard electrical fires are common, but in most cases these are 
small enough to be put out with a hand-portable extinguisher. The most severe 
fires generally are caused when ruptured high-pressure hoses spray flammable 
fluids (class B fires) onto hot surfaces. The resulting fast-growing fire is 
difficult to extinguish and significantly impedes safe operator egress, espe- 
cially in larger trucks where the cab-to-ground distance can be as far as 
12 feet. A system using hardware developed for military and petrochemical 
applications was installed and tested on a 100-ton haulage truck at the Cyprus 
Pima mine near Tucson, Ariz. 2 This first-generation prototype system, which 
protected the truck's engine and dynamic brake grids, used optical and thermal 
fire sensors to trigger stored pressure, dry-chemical extinguishers (fig. 3). 
Automatic controls with manual override were provided. A second prototype 
system was installed at the Erie mine near Hoyt Lakes, Minn., for cold-weather 
testing. These tests culminated in actual fire tests (fig. 4) and demon- 
strated that such automatic systems are feasible. 

The long-term ruggedness and reliability of these first-generation sys- 
tems were evaluated by installing a system that featured both optical and 
thermal fire sensing and stored pressure, dry-chemical suppression on a 120-ton 
WABCO bottom-dump coal hauler in the Jim Bridger mine near Rock Springs, Wyo. 3 

Dual fire sensing was selected to provide both rapid response and high 
reliability, while thermal sensors trade of f high reliability for slow detection. 

2 Johnson, G. A. , and D. R. Forshey. Automatic Fire Protection Systems for 
Large Haulage Vehicles. Prototype Development and In-Mine Testing. 
BuMines IC 8683, 1975, 16 pp. 

3 Stevens, Ralph B. Automatic Fire Sensing and Suppression Systems for Mobile 
Mining Equipment. BuMines Open Fire Rept. 34-79, January 1978, 166 pp.; 
research done under Contract No. H0262052 by FMC Corp., Santa Clara, Calif. 
Available for reference at Bureau of Mines facilities in Denver, Colo., 
Twin Cities, Minn., Bruceton and Pittsburgh, Pa., and Spokane, Wash.; U.S. 
Dept. of Energy facilities in Carbondale, 111., and Morgantown, W. Va. ; the 
National Library of Natural Resources, U.S. Dept. of the Interior, Washington, 
D.C.; and the National Technical Information Service, Springfield, Va., 
PB 294 731/AS. 




Control 
panel 



Extinguishers ^ actuator 

FIGURE 3. - First-generation prototype automatic fire protection system for haulage trucks. 




FIGURE 4. - Field test of automatic fire protection system for haulage truck. 



The two sensor types were used in tandem to combine the positive features of 
each. Four near- infrared optical flame detectors were mounted above and away 
from the mud-slinging tires and under the engine hood and A-frame to observe 
the exhaust and turbocharger areas. A thermister core thermal detection cable 
was used in tandem with the optical sensors, as described above. The 16-foot- 
long, 5/64-inch-diameter, steel-sheathed cable contained two electrical con- 
ductors separated by a semiconductor material whose electrical resistance 
varied sharply with the temperature. The resistance between the two conductors 
indicated temperature. (This extremely rugged sensor is common on commercial 
aircraft and marine vessels.) 

On the mine equipment, the heat sensing cable was arranged in a U-shaped, 
looped circuit with legs extending forward over the exhaust manifolds, then 
routed under the A-frame at the rear of the engine. An ambient temperature 
probe was installed near the truck ladder to automatically adjust the alarm 
set point of the thermal sensor up or down depending on the ambient tempera- 
ture. The control panel assembly consisted of an ON-OFF- TEST/RESET switch, 
audible and visual fire warning indicators, and a manual discharge button. 
The manual override discharge button initiated discharge of extinguishant 
even when the control panel power switch was off. Current was supplied 
directly by the vehicle's battery. If an optical sensor detected a fire, a 
yellow FAULT/FLAME warning light on the control panel illuminated, and the 
audible alarm sounded. No automatic discharge of the dry-chemical powder 
happened if fires were sensed only by the optical sensors. If the thermal 
device alone sensed a fire, the red FIRE warning illuminated, and an alarm 
sounded. The system automatically discharged the agent after a 10-second 
delay, during which time the driver could stop, turn off the engine, and test 
the system for malfunctions. Moving the control panel switch to TEST/RESET 
during the 10-second delay reset the discharge delay to provide an additional 
10 seconds after the control panel switch was released from the test position. 

When optical and thermal wire sensors detected a fire simultaneously, the 
dry-chemical powder was immediately discharged to suppress the probable flash 
fire situation. Immediate discharge also could be manually initiated by 
striking the discharge button. 

A remote system discharge switch, located at the base of the ladder, per- 
mitted manual actuation of the system without any fire signals, regardless of 
the position of the control panel switch or of the truck's master switch. 

The integrity of the control circuit constantly was monitored, and the 
operator was alerted to any electrical malfunction by the yellow light and 
pulsing horn. 

Multipurpose dry chemical (monoammonium phosphate) was selected as the 
fire suppressant agent. This agent is effective in suppressing class A, B, 
and C fires (ordinary combustibles, flammable fluids, and electrical), but is 
particularly effective on class B fires — the most common class of fires on 
haulage trucks. The agent was contained in two 25-pound-capacity cylinders 
pressurized to 500 pounds per square inch (psi) with dry nitrogen. A switch 
monitored nitrogen pressure, and if the pressure fell below 450 psi, a yellow 



fault light on the control panel illuminated. The cylinders were prepressur- 
ized to avoid caking of the dry chemical. Each cylinder was fitted with a 
solenoid valve to discharge the suppressant. 

The cylinders were housed in two protective enclosures mounted on the 
right front corner of the truck's operator deck. A manifold connected to the 
outlet port of each cylinder divided the flow of dry chemical through four 
flexible, steel-braid reinforced hydraulic hoses to fixed nozzles. Four 
nozzles from one cylinder had a 180° fan discharge pattern and were pointed 
to divide the flow of extinguishing agent to half above and half below the 
exhaust manifolds in the engine area. Two of the four nozzles from the second 
cylinder had the same fan pattern and were pointed to split equal flow over 
the transmission. The remaining two units were 360° cone-shaped nozzles, one 
pointed to the oil reservoir and one to the diesel fuel tank saddle mounted 
to the rear frame. A schematic of the system design is shown in figure 5. 

The system was installed on the bottom-dump coal hauler in January 1977 
for a 10-month endurance test. After that time the system was fire-tested by 
applying a torch to the thermal wire sensor. An optical sensor detected the 
presence of flame immediately, and in spite of an ambient temperature of 40° F 
and cross winds through the engine area exceeding 40 mph, the thermal wire 
responded to the heat in approximately 30 seconds. The system then discharged 
and distributed sufficient powder to all protected areas of the machine (fig. 6) . 




Thermal wire 
sensor 



FIGURE 5. - Automatic fire protection system for coal haulers. 



10 




FIGURE 6. - Field test of automatic fire protection system on coal hauler. 

However, during this 10-month period, several weaknesses in the system 
design were identified. The system was susceptible to false alarms during 
periods of low vehicle-battery voltage. Although discharge of the suppressant 
did not occur, the fire and fault lights illuminated and the alarm sounded. 
In addition, inductive voltage or electrical transients occasionally cycled 
the system through the test sequence. Also, during the first 2 months of the 
endurance test, pressure was lost from the suppressant cylinders. Starting 
the third month of the test, the originally installed neoprene seals in the 
solenoid valve were replaced with specially manufactured cast urethane seals, 
which corrected this problem. The optical sensors proved unreliable due to 
dirt buildup on the lenses. The optical sensor that detected the flame during 
the fire tests of the system responded only because its lens had been wiped 
clean just prior to the test. During previous in-mine tests of this sensor, 
false alarms caused by red sunsets, welding, etc., were a problem. However, 
no false alarms attributable to the optical sensors were encountered during 
this test program, probably due to the rapid buildup of dirt. 

FIRST-GENERATION SYSTEM DESIGN MODIFICATIONS 



The fire protection system design described above also was tested on a 
170-ton WABCO ore haulage truck at the Cyprus Pima mine near Tucson, Ariz. 
This second system was identical to the one tested on the coal hauler at the 
Jim Bridger mine. 



11 



The installation was made under a service contract to FMC Corp. in 
January 1977. After 7 months of operation on the truck, the system was con- 
verted from stored-pressure to cartridge-activated extinguishers because of 
recurring losses of pressure from the originally installed stored-pressure 
units, and to test a specially designed cartridge puncturing device. Manually 
activated fixed fire suppression systems are common on this type of equipment. 
Such a cartridge puncturing device would allow mine operators to convert their 
manual systems to automatic operation. The cartridge-activated suppression 
system consisted of the solenoid operated, gas cartridge puncturing device 
(fig. 7), and two nonpressurized 25-lb dry-chemical extinguishers. When sup- 
plied with an electric current, the solenoid actuated, releasing a spring- 
loaded puncture pin. The puncture pin pierced the brass seal of a high-pressure 
nitrogen cartridge. The nitrogen was carried to the extinguishers through a 
fixed network of hoses to eight discharge nozzles. A schematic drawing depict- 
ing the layout of the system is shown in figure 8. (As noted above, the prob- 
lem of pressure loss was later corrected on the coal hauler with the use of 



Drive spring plug 



Drive spring 



Plunger 




Solenoid 

End cap 

Spring 



Puncture pin 

FIGURE 7. - Automatic fire protection system actuation device. 



12 



Extinguishers 




Engine 
area 



Control 
panel 



Ambient 

temperature 

probe 



Manual 
actuator 



FIGURE 8. - Automatic fire protection system for haulage vehicles. 

improved ure thane valve seats.) Following this conversion, the system under- 
went continuing endurance tests until the test vehicle was removed from pro- 
duction service in November 1977. 

Field performance of this system closely paralleled that of the one on 
the coal hauler. Pressure loss from the extinguishers and dirt buildup on the 
optical sensors were the principal operational problems. However, unlike the 
coal hauler system, electrical transients did not interfere with system per- 
formance. The system was discharged once by a mine mechanic who mistook the 
ground level remote manual discharge switch for a truck ladder light switch. 

OPTIMIZED SYSTEM DESIGN 



Due to problems of pressure loss from prepressurized extinguishers and 
dirt on optical sensors (as described above) , and to reduce the cost and com- 
plexity of the system, a third design was developed which used cartridge- 
activated extinguishers and thermal wire sensing alone. Two systems were 
developed and tested based on this conceptual design: One by the FMC Corp. 
(see footnote 3) on an ash haulage truck at the Jim Bridger mine, and the 
other by Bureau of Mines personnel on a 100-ton haulage truck at the Reserve 
mine near Babbitt, Minn. (fig. 9). These systems were specifically designed 



13 



Fire extinguishers 
Thermal sensor 



Nozzle 




Hand portable extinguisher 



Control panel with manual 
actuator 



Hand portable 
extinguisher 

FIGURE 9. - Automatic fire protection system with thermal fire sensing only. 

to retrofit automatic actuation to an existing manual system. Thermister core 
thermal wire was again used as the fire sensing element, and the suppressant 
was supplied by cartridge-activated extinguishers. The control system was 
similar to those described previously. The heat sensing wire, control box, 
and suppressant nozzles were mounted as they were on the coal hauler. The 
actuation device was mounted under the left front fender. The ground level 
manual actuator was mounted near the base of the ladder. 

The system at the Jim Bridger mine was fire-tested in November 1977 by 
applying a torch to the thermal wire sensor. The system sensed the fire 
within about 60 seconds and automatically discharged the fire suppressant 
agent (fig. 10) . Good dry-chemical coverage was obtained despite 40 mph 
crosswinds through the engine area. 

During the 9-month endurance test period, the control system was found 
to be sensitive to low voltage. The problem occurred only when the engine was 
off and the lights were on. Low voltage caused the fire alarm system lights 
to illuminate dimly and the system to sound a weak, audible alarm. 

Several discharges of the system occurred during the test program as a 
result of manual activation by mine personnel unfamiliar with the system. 



14 







FIGURE 10. - Test of automatic fire protection system on ash hauler. 

FIRE WARNING-ONLY SYSTEM 



As a low-cost alternative to an automatic system, and in response to mine 
operators desiring more manual control over the fire protection system, a 
warning-only system was developed by the Bureau of Mines to be used in conjunc- 
tion with a manually activated fixed fire suppression system. This system 
gives the vehicle operator early warning of a fire condition, but it does not 
automatically activate a fire suppression system. Thus, if vehicle operators 
are not present or should they panic during fire emergencies and fail to acti- 
vate the fire protection systems, fire suppressant will not be discharged. 
This warning-only system consists of a thermister core thermal sensing cable 
connected to a cab-mounted control box. The control box is fitted with visual 
and audible fire alarms and a system circuit integrity test switch. This sys- 
tem was installed on a 100-ton Unit Rig haulage truck at the Reserve taconite 
mine near Babbitt, Minn., in May 1977. The control box was installed directly 
onto the vehicle dashboard to the right of the driver, with the manual fire 
protection system activator bolted to the top of the box. The sensor wire was 
looped through the truck's engine area (fig. 11) from mounting clips attached 
to the vehicle frame. The system was functionally tested following the instal- 
lation and at 4-month intervals thereafter. 

The system functioned without failure during an 18-month endurance trial 
period. 



15 




Control 
panel 



FIGURE 11. - Fire warning system for mine haulage trucks. 

NONELECTRIC AUTOMATIC SYSTEM 

A totally nonelectric automatic fire sensing and suppression system was 
tested on two mine haulage trucks via a memorandum of agreement between its 
manufacturer, the Ansul Co., of Marinette, Wis., and the Bureau of Mines from 
1975 to 1977. To avoid dependence of the system on complex and sometimes 
unreliable vehicle electrical systems, the Ansul Co. developed a fusible plas- 
tic tube sensing system that triggers cartridge-actuated, dry-chemical extin- 
guishers by a pneumatic signal. The fire detector consists of three elements: 
detection tubing, a pressure makeup device (PMD) , and a detection actuation 
device (DAD) (fig. 12). The detection tubing, DOT-approved nylon (1/4-inch OD) , 
is strung between the PMD and DAD so that it passes through all fire hazard 
areas to be protected. A high-pressure (1,800 psi) nitrogen gas cartridge is 
then attached to the PMD, pressurizing the detection tubing through a regu- 
lator to about 80 psi. As the detection tubing loses pressure through slow 
leaks at connections (which are almost impossible to avoid) , the PMD auto- 
matically "bleeds" in nitrogen from the high-pressure cartridge to maintain 
the 80 psi in the tubing. This pressure acts on a piston/puncture pin assem- 
bly in the DAD to compress an actuation spring. When the heat from a fire 
softens the detection tubing (at about 355° F) , the internal gas pressure 
causes the tube to burst. The rapid release of gas allows the actuation 
spring force to overcome the nitrogen pressure on the piston in the DAD, caus- 
ing the puncture pin assembly to pierce the brass seal of a second high- 
pressure nitrogen cartridge. This gas operates a cartridge-actuated, fixed 
dry-chemical suppression system. The system may also be manually activated. 



16 




High-pressure 
N 2 cartridge 



FIGURE 12. - Totally nonelectric fire sensing and suppression system. 

Both hot-weather and cold-weather in-mine tests of the system were per- 
formed to determine the rate of pressure loss from the PMD cartridge. One 
system was installed on a 150-ton ore haulage truck at the Pinto Valley copper 
mine in Arizona. A second system was installed at the Minntac taconite mine 
in northern Minnesota. Gas pressure inside the PMD's of each system was mea- 
sured daily with a pressure gage on the high-pressure side of the regulator. 
Readings were taken on the Pinto Valley system for 17 months and on the 
Minntac system for 2 months. Pressure loss was approximately 2.5 psi per day 
at Pinto Valley, indicating that a new PMD cartridge would be required after 
about 24 months of use. No pressure loss was observed on the Minntac truck. 



Haulage truck automatic fire sensing and suppression systems are now 
commercially available from several suppliers at prices from $850 to $5,000 
depending on design and capability. 



17 



This technology has been adapted for use on a wide variety of surface 
mining equipment. Complete systems have been designed, fabricated, and 
in-mine tested on dozers (fig. 13), front-end loaders (fig. 14), hydraulic 
excavators (fig. 15), blasthole drills (fig. 16), and power shovels (fig. 17) 



Thermal fire 
sensor 



Control panels 



Dry powder 
extinguishers 



Engine 
compartment 




Transmission area 



FIGURE 13. - Automatic fire protection system for mining dozers. 



18 




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Lubricant storage thermal sensor 



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Dry chemical nozzle 
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System activator 

Dry themical extinguisher 




Electrical cabinets thermal sensor 
Warning horn 

Manual discharge control 
Control box 



Fan control 



Motor - generator set thermal sensors 



Collector ring/ roller path area 



FIGURE 17. - Automatic fire protection system for power shovels. 



22 



IMPROVED VISIBILITY SYSTEMS 
by 
Guy A. Johnson 1 



ABSTRACT 

Visibility from the cab of a large haulage truck is a major mine safety 
problem because of the driver's limited field-of-view apparatus on the radi- 
ator deck. This problem is causing an increasing number of surface mine acci- 
dents as haulage trucks become larger. As a result, the Bureau of Mines has 
developed and in-mine tested prototype hardware that cost-effectively 
increases an operator's field-of-view from about 35 pet of where he has to 
drive to about 80 pet. This "improved visibility system" consists of fresnel 
lens blind area viewers, improved right- and left-hand mirrors, and ruggedized 
closed-circuit television. This report describes these components and deline- 
ates their on-truck testing. 

INTRODUCTION 

Large, rear-dump haulage trucks have a problem with restricted driver 
field-of-view. A driver cannot see large areas near his truck because he is 
set back under the truck box lip for protection from falling rocks and also 
because of auxiliary equipment on the radiator deck. These blind areas can 
conceal mine utility vehicles, pickup trucks, cars, people, road hazards, etc., 
and cannot be eliminated by present visibility aids (mostly mirrors) . The 
visibility problem is greatest in the right-front and rear areas of typical 
trucks, as seen in figure 1. Improved driver visibility would reduce accident 
potential and improve control (thus productivity) from the vehicle. 

To help solve this problem (which is growing as haulage trucks become 
larger), an improved visibility system was developed by the Bureau of Mines. 2 
The system consists of fresnel lens blind area viewers, a quick-change left 
mirror, a rectangular convex right mirror, and a ruggedized closed-circuit 
television (CCTV) system. The left mirror is 9 inches wide by 27 inches high, 

fining engineer, Twin Cities Research Center, Bureau of Mines, Twin Cities, 

Minn. 
2 Hawley, Kent W. , and Slade F. Hulbert. Improved Visibility Systems for Large 

Haulage Vehicles. BuMines Open File Rept. 100-78, April 1978, 121 pp.; 

research done under Contract No. HO262022 by MBAssociates , San Ramon, Calif. 

Available for reference at Bureau of Mines facilities in Denver, Colo., 

Twin Cities, Minn., Bruceton and Pittsburgh, Pa., and Spokane, Wash.; U.S. 

Dept. of Energy facilities in Carbondale, 111., and Morgantown, W. Va. ; 

the National Mine Health and Safety Academy, Beckley, W. Va.; the National 

Library of Natural Resources, U.S. Dept. of the Interior, Washington, D.C.; 

and the National Technical Information Service, Springfield, Va. , 

PB 286 065/AS. 






80 ft 



M 



FIGURE 1. - Typical restricted visibility of large-truck drivers. 



with a small convex mirror attached. It provides a good view of the left 
roadway area (including orientation features such as the left rear tire and 
the top left edge of the load bed). The right-hand mirror assembly contains 
a 12- by 16-inch rectangular convex (spherical) mirror with a 20-inch radius. 
The rectangular mirror shape gives an efficient view while being compact pro- 
tection. The unique blind area viewer is used to see the blind areas forward 
of and to the right of the truck (fig. 2). Three such viewers are used on a 
typical large (+100 tons capacity) truck. They are mounted on the truck's 
radiator deck. Each viewer increases the driver's downward visibility by 70°, 
so as to show objects within 5 to 10 feet in front of the truck (as opposed to 
the usual 60- to 70- foot-deep blind area). The viewer is a three-element, 
fresnel lens that gives an oriented 85° vertical and 60° horizontal angle. 
The CCTV component gives the driver a view from the rear similar to a car's 
rear-view mirror. The hardware consists of a ruggedized camera enclosure with 
a semiautomatic lens-window cleaning system. The television camera enclosure 
is a tubeless charge-coupled type that uses only 5 watts of power at 12 volts. 
It has a wide-angle, automatic iris lens for extended light range. The tele- 
vision monitor has a standard 9-inch picture reversed right-to-left for rear- 
view orientation. 



24 



Cab 

gpzzzzzzg 

Eye a. 

point | 



Blind area 
viewer device 




Gra de 



FIGURE 2. - Haulage truck downward visibility. 



This improved visibility system eliminates about 85 pet of the forward 
and right blind area, and about 95 pet of the rear blind area, which covers 
most of the ground areas with a history of restricted visibility accidents. 
The system's prototype hardware has been shown to be effective during a short- 
term test on a 150-ton truck. Current, long-term in-mine testing of second 
generation systems will delineate this technology's effectiveness, maintenance 
requirements, and user costs. Details of each of the system's components are 
given below. 

IMPROVED MIRRORS FOR LARGE HAULAGE TRUCKS 



After analyzing vehicle visibility hazards, it was decided that better 
mirrors are one of the most effective approaches to improved driver field-of- 
vision in terms of view characteristics and cost. Mirrors must reflect or 
turn light 10° to 180° to provide a useful view. In almost all vehicle appli- 
cations the view is reflected 60° to 175°, and some of the vehicle must be 
included in the view for orientation. It is also common to include the hori- 
zon or distant ground features in the view to aid orientation. The following 
are involved in the optical capabilities of mirrors: 

1. The field-of-view increases when the viewer is closer to the mirror- 
It increases with larger size mirrors. It decreases when the mirror is 
rotated away from the viewer. And, it increases by the amount of convex 
mirror curvature (in terms of degrees of arc across the surface) . 

.2. The image size increases as the viewer gets closer. It decreases as 
the object in view gets further away. And it decreases when convex mirrors 
have a small radius of curvature. 



25 



3. The ability to detect possible hazards increases with a larger field- 
of-view. It increases with larger image size. It decreases in low-contrast 
situations (for example, dust or fog). It increases with area illumination. 
It decreases with mirror surface distortion. And, it increases with frequent 
use. 

Of the various materials used to make mirrors installed on haulage trucks, 
glass gives the least distortion in both flat and convex shapes, even though 
convex mirrors with polished steel surfaces are common, and clear plastic 
mirrors (interior surface silvered) are used in a few mining operations. All 
convex mirrors distort images by curving straight lines; however, polished 
steel mirrors often have wavy line distortion that becomes significant when 
pitting, scratching, and denting degrade the surface. Polished steel mirrors 
can survive load-bed spillage that would destroy glass. Clear plastic mirrors 
can be scratched by load spillage and improper cleaning. 

A survey of mirror replacements showed that the life of a mirror on a 
haulage truck ranges from 1 month to over a year. One mine reported as many 
as eight 5- to 12-inch mirrors were replaced each shift for approximately 
100 vehicles of all types. 

The left mirrors are usually mounted from 18 to 42 inches from the driver, 
attached to the cab door or the left side of the cab. A few are attached to 
the cab deck railing. All mirrors are mounted far enough out to give a view 
of the left side of the load bed. In general, left mirrors are positioned to 
view the horizon and either the ground at the rear tire or the top edge of the 
load bed. The horizontal field-of-view depends on the distances to the oper- 
ator and the mirror's width, which usually ranges from 5 to 10 inches with 
field-of-view from 3° to 20°. 

Because the left mirrors are relatively close to the driver, image size 
in flat mirrors is slightly less than their actual size as seen from the 
actual distances. The vertical image directly depends on the mirror's length, 
which ranges from 10 to 30 inches; field-of-view varies directly from 20° to 
45°. Mirrors longer than 20 inches can give a view of both the rear tire and 
the top edge of the load bed without requiring head movement. Flat rear-view 
mirrors on the left side can give adequate depth perception, vehicle orienta- 
tion references, and image size to position a vehicle when backing up; however, 
the field-of-view frequently does not contain enough ground references for 
this task. 

A few convex and combination flat and convex mirrors are used as left 
rear-view mirrors. Convex mirrors have an effective field-of-view ranging 
from 30° to 20° along the horizontal center line. In one mining operation, 
5-inch-diameter, round, convex mirrors are used. These mirrors are not to 
position the vehicle, since the image size is small and depth perception was 
difficult, but the wide field-of-view is useful in locating possible hazards. 
Nearly all mirrors used on the left side are glass mounted in a metal frame. 



26 



Most conventional right rear-view mirrors used on large haulage trucks 
are nominal 12-inch-diameter, round convex mirrors mounted from 13 to 24 feet 
to the right and up to 8 feet forward to the driver. Exceptions include a 
16-inch-diameter, round, convex mirror and some large, flat mirrors. 

The convex mirrors have radii of curvature from 15 to 3 inches, and the 
arc ranges from 18° to 45°. This results in images of 7 to 15 times smaller 
than direct view over the same optical path. 

Because of the reduced image size and the exaggerated distance cues, con- 
vex mirrors are rarely used to position a vehicle when backing. The distance 
between the driver and the mirror significantly hinders detecting the presence 
and location of objects. Mirror distortion, damage, reduced contrasts, and 
mud splatters degrade the effectiveness further. 

When flat mirrors are used on the right side, they range from 8 to 
10 inches wide and 24 to 36 inches long. The horizontal field-of-view does 
not exceed 3°, and the vertical field-of-view ranges from 5° to 12°. The 
image size is equivalent to a direct view over a distance equal to optical 
path including the distance to the driver. The small field-of-view inade- 
quately covers the right rear areas. 

IMPROVED LEFT MIRROR SYSTEM 

The left mirror system developed by the Bureau is a 9- by 27-inch plane 
mirror with a 3- by 5-inch rectangular convex mirror attached for a wide-angle 
view. The mirror is in an enclosure designed to withstand minor rock spills 
and to facilitate quick replacement. Although simple in appearance, this 
mirror has ideas and features that are not effectively used in existing 
mirrors . 

The left mirror has the following specifications and features: 

1. The field-of-view shows the left side of the truck, including the 
top edge of the load bed and the bottom of the rear tire. No head movements 
are required to see this vertical field. The horizontal field of the plane 
mirror is sensitive to its distance from the driver; a small rectangular con- 
vex mirror is attached to the mirror face in order to expand this view to 
greater than 40°. 

2. Orientation can be maintained when glancing from either top or bottom 
because the left side of the convex mirror does not interrupt the orientation 
features in the plane mirror. The convex mirror is mounted onsite to prevent 
it from masking any significant features. 

3. The plane mirror element is a standard glass mirror. The assembly 
will accept glass mirror elements from 1/8- to 3/8-inch-diameter, including 
tempered and safety mesh backed mirror glass. The rectangular convex mirror 
is a standard hardware item mounted with silicon-based sealant. 



27 



4. The frame is rugged and is topped with a 3/16-inch plate to prevent 
damage from minor rock spills. 

5. The mirror is mounted with its right edge in line with the load bed 
for best view orientation. 

6. The mirror assembly is attached to the mounting structure with 
3/8-inch bolts with rubber washers for positive alinement. 

7 . The rear plate can be removed by hand by releasing four latches for 
quick mirror element replacement. 

The left mirror assembly is shown in figure 3. All materials and com- 
ponents are off-the-shelf items. 



FRONT VIEW 



SIDE VIEW 



Plane mirror 
I 



Approximate^ 
level 



Convex mirror- 
s'' x 5" 



Frame 



/ 



/ 



A. 




Bracket Backing 
plate 




Mounting 
bracket and 
protective 
plate 



/-Frame 
¥ fi,_" 



(l/2'x|"/ 2 "x»/8 

angle) 



Mounting bracket 



9"x27' 

Note: Flexible molding not shown 

FIGURE 3. - Left mirror assembly. 



28 



IMPROVED RIGHT MIRROR SYSTEM 

The right mirror system developed by the Bureau is a rectangular-shaped 
convex mirror. It has superior field-of-view and orientation features and is 
more than equivalent to a larger diameter circular mirror. 

The right mirror system has the following specifications and features: 

1. The field-of-view shows the right side of the truck including the 
top edge of the load bed and the rear tire. This image of the truck's side 
can be compressed into only 20 pet of the view by alinement. The vertical 
view is approximately 60° and the horizontal field-of-view is greater than 25° 
from top to bottom. Circular convex mirrors can equal this only across the 
center. 

2. The image size is slightly above average for the mirrors in common 
use. Image recognition is improved by the orientation features. 

3. The mirror element is a 12- by 16-inch rectangular section of a 
spherical mirror. The radius of curvature is constant with a range of 20 to 
25 inches. 

4. The mirror element is constructed of tempered glass; however, plexi- 
glass can also be used. The mirror is backed by rigid, high-density foam that 
holds hardware for mounting by four bolts. 

5. The mirror enclosure is fabricated from 3/16-inch steel plate and is 
topped with a 1-inch rubber fender to prevent minor rock spills from causing 
damage. 

6. The mounting structure with its U-bolt attachment was designed for 
universal application without right handrail modification. Since alinement is 
fixed after installation, a simplified structure is feasible for specific 
truck models. 

7. The mirror face is mounted with the left edge in line with the load 
bed. It is also alined 60° out from the truck's side and 15° down from the 
vertical. The alinement will vary slightly for different trucks, but no 
adjustment is needed for individual drivers. Figure 4 shows the assembly of 
the right mirror system. 

Evaluation of the right mirror system in the lab and the field shows that 
the rectangular convex approach gives effective field-of-view with a consist- 
ent view orientation that does not vary significantly from truck to truck. 
The field-of-view is more than 100 pet wider than a standard 12-inch polished 
steel circular convex mirror. The components are not off-the-shelf yet, but 
MBAssociates is beginning production soon. 



29 



TOP VIEW 



SIDE VIEW 




Rubber 
protector 



Mounting 
frame 



Mirror enclosure 



-U-bolt and 
pipe 

mounting 
attachment 




Rigid foam 



Rectangular^ 

convex mirror 

I2"xl6',' 22"radius 

Mirror assembly 




•Mounting 
hardware 



FIGURE 4. - Right mirror assembly. 

RUGGEDIZED CCTV FOR BACKUP VISIBILITY 

An analysis of closed-circuit television (CC1V) applications on large 
vehicles showed that only one system had been recently used. The truck was an 
experimental model that has since been dismantled. The CCTV system (consist- 
ing of a cab-mounted monitor and two cameras) was used on a Marian V-CON, 
250- ton-capacity truck prototype in the early 1970' s to provide visibility for 
inexperienced drivers. One camera gave a rear view including the left rear 
tires; the other camera covered the right-side blind area. The following 
information about this novel system was obtained from informal discussions 
with technical personnel acquainted with the hardware: 

1. The system used standard, off-the-shelf components with no special 
modifications. 

2. A standard wide-angle lens was used on each camera. 

3. At night or in reduced illumination, some view detail could be main- 
tained with the monitor adjusted to maximum brightness. 

4. The CCTV system was useful to new drivers, but experienced drivers 
did not use it as much. 

5. Nothing prevented mud and dust accumulation, so the lenses needed 
frequent manual cleaning. 

3 Reference to specific equipment or trade names is made for identification 
only and does not imply endorsement by the Bureau of Mines. 



30 



A ruggedized CCTV system was developed by the Bureau for the rear blind 
area on the largest haulage vehicles. This system combined features that 
improved CCTV systems in the mine haulage environment. Details of the camera 
enclosure are shown in figure 5. This CCTV backup system has the following 
features: 



1. It operates under all lighting levels including night with automatic 
adjustment to light changes. 

2. The monitor is a standard closed-circuit model and cannot receive 
broadcast television channels. 

3. The camera is a charge-coupled, solid-state silicon-imaging device. 
Its enclosures can adapt to other vidicon-tube cameras. The camera is in a 
fixed mount and it has a wide-angle lens with an auto-iris. 

4. A lens window cleaning system will function on demand from the cab. 
The cleaning cycle is automatically timed and is initiated by a pushbutton 
switch in the cab. The lens window cleaning system is external to the camera 
enclosure, and its washer reservoir can be removed from the camera location 
for a lower profile. 



Fill cap 

vBreather 



Protective plate 

Washer nozzle 
Lens wiper 



<\Wiper park switch 




-Camera enclosure 
■CCTV camera 
tuntrng bracket 
-Cable coupler and brackets 

FIGURE 5. - CCTV camera assembly 



4-in-diameter glass- 



31 



5. The camera enclosure can be sealed from the outside environment. The 
design provides for the use of dry nitrogen purging or of desiccants. 

6. The system is powered by 12-volt or 24-volt dc sources. 

The camera and lens selected for use in the system have the following 
features: 

1. The charge-coupled camera operates on 12 volts dc, consumes only 
5 watts of power (less the auto-iris lens), and causes no heat problems. 

2. The camera with an auto-iris lens operates at normal and very low 
light levels without manual adjustments. The silicon imaging device has an 
antibloom feature that prevents lights, reflections, and the sun from obscur- 
ing the video picture. 

3. The camera with its lens is only 8 inches long, 4-1/2 inches wide, 
and 3 inches high. It weighs less than 4 pounds. 

4. The camera is mounted on a rubber pad and is ruggedized internally 
for protection from shock and vibration. For low-temperature operation, a 
thermostatically controlled tape heater is attached. No provisions for cool- 
ing are needed. 

The CCTV camera is an RCA TC1160 with a grade B silicon imaging device 
(SID 52501). The 5-1/2- by 5-1/2- by 17-inch enclosure can be adapted to 
other vidicon-type cameras; however, there is no alternate camera that is a 
direct replacement. With significantly different performance, an RCA 1025/SO5 
camera could be used. The CCTV monitor is a Setchell Carlson Model 6M917 
modified to operate on 24 volts dc. 

FRESNEL LENS BLIND AREA VIEWER 

The "blind area viewer" is an entirely new concept to apply to mine truck 
haulage. The viewer was developed to help a truck driver see into the blind 
areas to the front and the right. It is basically a fresnel lens (or flat 
lens) which has a downward-oriented, wide-angle view emphasizing the scene 
below the driver's unaided line of sight. This allows objects to be seen to 
within 5 feet of the truck. The right-side visibility improvement this 
creates is shown in figure 6. 

A commercially available, single-element fresnel lens for this applica- 
tion was evaluated early in this project; however, it gave only a 30° downward 
angle of view. The two elements of the current lens give a 70° downward angle. 
They are sandwiched between two panes of safety glass that protect the finely 
grooved lens from foulding dust and moisture. The lens/glass assembly is 
mounted in a rugged enclosure to protect it from rock spills (fig. 7). 
Louvers in front of the lens prevent glare. The viewer is mounted perpendicu- 
lar to the driver's line of sight and can be tilted away from the driver to 
optimize the optical qualities by reducing light losses. 



32 



Area of visibility 
improvement 

Grade horiz 




Lens 
enclosure 



FIGURE 6. - Improved field-of-view due to blind area viewer. 



Rubber 
protector 



Mounting 
bracket 




Lens retainers with 
rubber mouldings 







Fresnal lens 
unit I2"x 14" 

Safety glass 




Glare- 
control 
louvers 



FIGURE 7. - Blind area viewer assembly. 



33 



The fresnel lens blind area viewer has the following features and 
specifications : 

1. The fresnel lenses are pressed into plastic plates composed of cellu- 
lose acetate butyrate and have a design life of 5 years. Each unit is 12 by 
14 by 1/8 inches. 

2. The two elements of the lens contain three linear echelon analogs of 
a cylinder lens. 

3. The field-of-view is 70° downward and 15° upward. The horizontal 
field-of-view is 60°. The lens emphasizes the view between 30° and 50° 
downward . 

4. The lens assembly has an estimated light loss of between 15 and 20 pet. 
This light loss cuts image contrast and increases sensitivity to glare. 

5. Glare must be controlled for effective use of the fresnel lens assem- 
bly. The best approach that does not increase light losses is to prevent 
direct sunlight or direct lighting from contacting it; this requires glare- 
control louvers on the front. 

ON- TRUCK DEMONSTRATION 

To evaluate the credibility of all components of the improved driver 
visibility system (fig. 8), a mockup system was tested at the contractor's 
facilities and at Kaiser Steel's Eagle Mountain mine in southern California. 

The first mockup demonstration was conducted on the rooftop of a single- 
story building (which simulated the placement of the visibility aids on a 
large truck). This test conducted in spring 1977 was attended by Bureau of 
Mines technical personnel, Mine Safety and Health Administration officials, 
and mining industry representatives. 

The field test occurred in July 1977 on a 170-ton truck (fig. 9). The 
prototype system was installed on the truck during routine preventive mainte- 
nance, and the truck was then returned to active production for 8 days. Then 
the truck was pulled out of production, and all visibility aids were inspected 
for damage and cleanliness. Only one problem was detected. A relay in the 
CCTV lens cleaning system had fused closed and burned out the washer pump. 
This was repaired by substituting a relay with a higher current rating. 



34 



Blind area 
viewers 



T V monitor 

Left rear _ 
view mirrors 



Right rear 
view curved 




FIGURE 8. - Improved visibility system. 



35 




FIGURE 9. - In-mine testing of the prototype hardware. 

The driver's visibility limits were then delineated using white tiles on 
the ground to show the previously existing blind areas. Flags on fiberglass 
poles showed the 5-foot-high visibility limits. Figure 10 shows the improved 
driver visibility resulting from the system. 

At the ready line both the oncoming and offgoing truck drivers were 
interviewed for their opinions and suggestions. All drivers liked the system. 



After an afternoon break, a nighttime demonstration similar to the static 
demonstration was conducted. The blind area viewers and CCTV system were then 
removed. At the mine's request, the improved mirrors were left on. 



36 




FIGURE 10. - Increased visibility with improved visibility system. 



LONG-TERM IN-MINE TESTING 

The Bureau of Mines is currently on-vehicle testing second-generation sys- 
tems on 10 trucks in three surface mines. This testing will last a minimum of 
a year. The mines cooperating with the Bureau and its contractor, MBAssociates , 
in this test program are Kaiser Steel's Eagle Mountain mine, Eagle Mountain, 
Calif., and Erie mine, Hoyt, Minn.; and AMAX' s Belle Ayr mine, Gillette, Wyo. 

COST-EFFECTIVENESS ANALYSIS 

This project sought to develop concepts that would involve costs accept- 
able to mine operators. Thus, cost-effectiveness of each improved visibility 
aid was considered in its design. 

Component costs and fabrication, assembly, and installation time for the 
first-generation improved visibility system are shown in table 1. These esti- 
mates are based on reproducing of the prototypes in quantities of 10 to 100 units. 
A range of costs was included to account for quantity price discounts, component 
options, and price variations. The initial costs of the improved mirror systems 
and the blind area viewer are close to what mine operators pay for existing mir- 
rors (with brackets and mounting structure). The CCTV rear-viewing system has a 
relatively high cost, which may be acceptable only for the largest haulage trucks. 



37 












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38 



The most tangible benefit of the system is a considerable increase in a 
driver's field-of-view, which increases his ability to avoid collisions. 
There is also considerable reduction in damage to tires, equipment, and struc- 
tures. The benefits will vary at each mine. An example of an intangible 
benefit is reduced driver fatigue and stress and increased confidence. With 
first-hand knowledge of the losses and safety problems, each mine operator can 
best assess the potential value of an improved visibility system. 

The maintenance costs for the improved mirror system should be lower than 
those for existing mirrors, and their effectiveness should be greater. The 
view provided by the blind area viewers has not comparison with that provided 
by existing systems. The additional cost, if any, would be justified by the 
coverage of a blind area that has a history of a high accident frequency. The 
viewer is a nonpowered, very low maintenance device. The cost-effectiveness 
of the blind area viewer is definitely sufficient to warrant its use. 

The cost of the CCTV system is high compared to that of nonpowered 
devices. The system was developed for trucks larger than 170 tons to prevent 
direct backing collisions and to prevent backing through dump berms with the 
right wheels. The CCTV system will be cost-effective in mines where backing 
accidents are a safet> problem. The initial cost should drop considerably as 
the cost of image cameras drop. The CCTV system's initial and long-term cost 
is equivalent or less than the cost of several drive-train, steering, and 
braking safety devices. 

CONCLUSIONS 

The improved visibility system greatly increased the field-of -vision of 
the driver and adds a degree of safety not present with existing systems. 
Each visibility aid was developed after analysis of the restricted driver 
visibility problem. A short-term, in-mine test showed that these visibility 
aids provided the necessary improvements. To further evaluate driver accept- 
ance, reliability /maintainability , and safety potential, long-term on-vehicle 
testing is being conducted on second-generation prototype systems. 

Left-Hand Mirror . — The left mirror component provides the driver with 
both a wide-angle and a plane mirror view that includes all the visual orien- 
tation cues needed for backing. It is sized for its application and designed 
for easy, "quick change" replacement of the mirror. For night use, illumina- 
tion of the area behind and to the left of the rear tires with normal backup 
lights is needed for backing. 

Right-Hand Mirror . — The right mirror gives a reliable, optimally shaped 
view of the right rear side of the truck. Once installed, it does not need 
to be adjusted. Its field-of-view is more than a 100 pet larger than that of 
currently used mirrors; it is less vulnerable to rock spills and compact 
enough to allow tight clearance. Its dimensions and radius can be increased 
up to 25 pet for larger trucks but only with special fabrication. Although 
the present mounting brackets tend to swing away on impact with structures, 
this feature is being improved by a "swing-away" feature in the second- 
generation designs. 



39 



Blind Area Viewer . — The fresnel lens blind area viewer provides the 
normally oriented view of areas within 5 feet of the truck with a 60° field- 
of-view. This view covers an area of frequent accidents. The viewer is par- 
ticularly effective in detecting high-contrast objects such as helmets, 
painted vehicles, and lights. For low-contrast objects, it is sensitive to 
lighting conditions, so improved shielding from glare and stray light are 
added to the second generation. 

During the short-term, on-truck test, driver responses were favorable; 
however, view interpretation requires an adjustment period. 

CCTV System . — The CCTV system is a method of direct rear vision for 
rear-dump haulage trucks larger than 170 tons. In the system's field demon- 
stration, its low light capacity, antiblooming feature, and lens washing 
system provided a clear view in the most severe mining conditions. The short- 
term demonstration has shown a need for improvements, particularly regarding 
installation and fabrication efficiency. The second-generation prototype 
system has been simplified, and both a warm climate and cold climate model 
have been developed with ruggedized enclosure. The hardware is relatively 
expensive, but mines with certain backup/high dump problems have contacted the 
Bureau and are willing to work with us to reduce the hardware cost to make 
this system cost-effective. 

More Information . — Detailed information about the prototype improved 
visibility system is available from the contractor's final report (see foot- 
note 2). Information about the ongoing collision protection work is also 
available from the Twin Cities Research Center, P.O. Box 1660, Twin Cities, 
Minn., 55111. 



40 



IMPROVED INGRESS /EGRESS SYSTEMS FOR LARGE HAULAGE TRUCKS 
Development and In-Mine Testing 
by 
David A. Johnson 1 



ABSTRACT 

Slip and fall accidents are the major cause of lost-time injuries associ- 
ated with large haulage trucks. An evaluation of the safety hazards associated 
with ingress and egress on these vehicles showed that most of the accidents 
occurred near the bottom of the ladder. The major hazardous design conditions 
were identified as excessively flexible supports for lower steps or rungs, 
inappropriate ground-level-to-first-step distances, poor step designs, and 
inadequate handrail and guardrail designs. Additional hazards are intro- 
duced by the lack of proper maintenance of ladder hardware and the work 
practices of operators in carrying articles onto the truck. Several improved 
ladder designs were designed and tested, which are currently undergoing long- 
term testing in operating mines. 

INTRODUCTION 

The principal cause of lost-time injuries on mobile mining machines used 
in surface mines is slips and falls while ascending or descending the machines. 
Slips and falls constitute over one-third of all lost-time accidents associa- 
ted with haulage trucks. While these accidents are typically minor in sever- 
ity, they result in substantial amounts of employee lost time and lost 
productivity. No fatal accidents have been identified as the result of a 
slip or fall from a haulage truck ladder while the vehicle was stationary. 

Slip and fall accidents are prevalent in both metal/nonmetal mines. 
These accidents do not appear to be influenced significantly by geographic 
location, weather conditions, or time of year. However, there does appear 
to be a time-of-day influence: the majority of the slips and falls occur 
during the first shift. This may be because more employees work the first 
shift and more maintenance operations are performed during the first shift. 

Haulage truck manufacturers and mining companies both recognize the 
problem of ladder safety. To date, as evidenced by the accident statistics, 
no effective solutions to the problem appear to have been found. The lack of 
effective guidance in the design of ingress and egress systems has hampered 
progress. In most cases, the ladder appears to be added as an afterthought in 
the hauler design. In short, the stringent system design concepts employed 

fining engineer, Twin Cities Research Center, Bureau of Mines, Twin Cities, 
Minn. 



41 



on most of the machine features are not generally applied in ladder access 
system designs. 

This project, conducted by Woodward Associates, Inc., and sponsored by 
the Bureau of Mines Twin Cities Research Center, was designed to accomplish 
the following objectives, relative to large rear-dump vehicles in the 100-ton- 
and-larger class: 

1. Evaluate the safety hazards associated with routine mounting and dis- 
mounting of the vehicles and during egress in emergency situations. 

2. Establish guidelines for improved ladder systems. 

3. Develop improved ladder designs. 

4. Select the most promising designs and perform preliminary evaluation 
tests. 

5. Conduct in-mine tests on actual haulage vehicles. 

SAFETY HAZARD ASSESSMENT 

A review of a large number of operating haulage vehicles identified the 
following significant ingress and egress system design deficiencies: 

1. Inadequate handrail and guardrail designs, which increase the 
difficulty of mounting and dismounting the vehicle (fig. 1) . 

2. Excessively flexible lower section supports for lower steps or rungs, 
thus making ascent or descent difficult and hazardous. 

3. Inappropriate ground-level-to-first-step distances, which also create 
difficulties and hazards (fig. 2). 

4. Poor step designs that permit mud, snow, ice, grease, and oil 
accumulations and thus result in hazardous footing (fig. 3). 

The lack of proper maintenance of ladder hardware (fig. 4) also increases 
the safety hazard. The location of a ladder at a front corner of the vehicle 
makes it more vulnerable to damage. Most of the damage to steps and rails 
occurs in the lower portions of the ladder structure and is usually caused by 
collision with earthwork, high walls, berms, or boulders. 

The work practices of operators in carrying articles on and off the trucks 
introduce additional hazards. Operators commonly carry lunch boxes, thermos 
bottles, seat cushions, jackets, etc., onto the truck. 

Discussions and visits with mine operators and original equipment manu- 
facturers identified vehicle fires as the sole situation that was sufficiently 
critical to warrant an emergency exit on the part of haulage vehicle operators. 
An individual in other emergency situations, such as imminent rollover, may 
also instinctively attempt vehicle egress. 



42 




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44 




FIGURE 4. - Example of typical damage to upper section of a hauler ladder. 



45 



DESIGN GUIDELINES 

Research indicated that the greatest overall improvement in safety would 
be achieved by making the following changes to ingress and egress systems: 

1. Redesign . The lower portions of existing ladders must be redesigned 
to reduce movement during usage and to reduce the distance between the ground 
level and the first step. 

2. The ingress and egress systems must be brought into conformance with 
the SAE J185a design recommendations. 

3. Designs with an angle of inclination of greater than 60° must require 
the use of both hands for safe use in order to conform to the SAE J185a. 
Proper handrails must be provided. 

4. In addition, a method must be required to lift articles onto hauler, 
or else management policies must be established to prohibit items such as 
lunch boxes from the hauler. 

IMPROVED LADDER DESIGNS 

Two design configurations were developed for the lower portion of ladders. 
These designs are described briefly below: 

1. Four-Spring Mounted Lower Steps (fig. 5). This design uses a basic 
four-bar linkage in a lower step assembly. Pretensioned, solid wound, 

FOUR SPRING SUPPORTED LOWER STEPS 



RIGID LADOER 
ASSEMBLY - 



HI-GRIP STEP 



PRETENSION SPRING 
ASSEMBLY (TYPICAL) 




MATERIAL (TYPICAL) 

FIGURE 5. - Four-spring lower steps on a conventional ladder system. 



46 



SINGLE SPRING SUPPORTED LOWER STEPS 




RKJIO LADDER 
ASSEMBLY 



HIGH GRM» STEP 
MATERIAL (TYPICAL) 



FIGURE 6. - Single-spring center tube mounted lower steps. 

extension springs fabricated from high-strength steel are the support 
elements. 

2. Single-Spring Center Tube-Mounted Lower Steps (fig. 6). This 
design consists of lower steps welded to a rectangular central tube that 
incorporates an omnidirectional pivot point. An elastomer plug within the 
central tube keeps the rectangular tubes from rotating and shifting laterally. 
The two sections of tube are held together as an assembly by a spring/cable 
arrangement. 

PRELIMINARY EVALUATION TESTS 



Several primary ladder lower step designs were subjected to human factors 
field evaluation and structural testing demonstrations at the Cyprus Pima 
mine, Tucson, Ariz., in September 1978. 

It was concluded that the four-spring (figs. 7-8) and single-spring center 
tube (figs. 9-10) designs could appreciably reduce slip and fall accidents. 
These units were especially effective for reducing first-step height, increas- 
ing stiffness of the ladder during normal ingress and egress and maintaining 
continuity of step and distance and angle of inclination of the ladder. Wide 
acceptance could be expected by the mining companies and equipment manufacturers 



47 




FIGURE 7. - Four-spring lower step on a 170-ton rear dump hauler. 




FIGURE 8. - Four-spring lower step during damage tolerance testing. 



48 




FIGURE 9. - Single-spring center tube system on a 170-ton hauler. 




FIGURE 10. - Center tube system being damage tolerance tested. 



49 



because the improvements can be retrofitted to existing trucks or included in 
the original design of new trucks at a reasonable cost. In addition, mainte- 
nance and repair costs of ladder systems on large haulage trucks can be 
expected to be substantially reduced. 

EMERGENCY EGRESS 

A secondary objective of this program was to evaluate emergency egress 
systems and, if any were found to be desirable, to complete the design, 
fabrication, and testing on a mine vehicle. 

Extensive discussions and visits with mine operators and original equip- 
ment manufacturers identified vehicle fires as the sole situation that was 
sufficiently critical to warrant an emergency exit on the part of haulage 
vehicle operators. An individual, however, in other emergency situations 
(that is, imminent rollover) may instinctively attempt vehicle egress. Where 
primary egress devices that are protected from the potential hazard (for 
example, fires) cannot be provided, acceptable emergency egress systems are 
necessary. 

The following criteria were established for emergency egress systems: 

1. Must accommodate variations in operator capabilities. 

2. Must demonstrate high reliability. 

3. Must require low maintenance over a reasonable lifespan. 

4. Should not be "an attractive nuisance," present an enticing challenge, 
or invite operators to "try it." 

5. Must require operator training, and be safe enough for such training. 

6. Must be conveniently located for the defined emergency situations. 

7. Must not interfere with normal ingress and egress or be used as a 
substandard normal system. 

8. Must function under all adverse mining conditions. 

9. Must limit operator use to zero vehicle speed in either forward or 
reverse direction. 

Two emergency egress systems were evaluated as most closely meeting these 
criteria, the telescoping ladder systems and the controlled descent reel 
system. Both are currently available in the marketplace. Testing and demon- 
stration showed the controlled descent device (fig< H) to be the superior 
approach. The device demonstrated high user acceptance, provided ease of 
retrofit, has inherent safety advantages over the telescoping unit, and is 
commercially available at a moderate cost. 



50 




CONTROLLED DESCENT EMERCENCV EGRESS 



HOPE STORAGE 
HEEL 




FIRE+OSTE 
ACTIVATION 

FIGURE 11. - Controlled descent emergency egress system. 

Inquiry data collected by the Health and Safety Analysis Center, Mine 
Safety and Health Administration, in 1977-78 for emergency jumps from haulage 
trucks of all sizes total 65 jumps. Of these, 10 were due to vehicle fires, 
and the rest were vehicle- in-mot ion situations (that is, loss of steering, 
loss brakes, engine killed on grade). No fatalities were attributed to fires, 
but three fatalities resulted from vehicle- in-mot ion emergencies. 

As a result of this research, the following conclusions about emergency 
egress systems were developed: 

1. With the exception of uncontrolled fires and driving into deep water, 
the safest place for the operator is in the cab, with the seat belt securely 
fastened. 



2. The best emergency system for fires is a well-designed, well- 
maintained fire detection and suppression system on each truck. Adequate 
operator training should be provided for fire situations and for when the 
truck is driven into deep water. 



51 



CONCLUSION 

Following successful demonstration of the new ladder designs at the 
Kennecott Bingham Canyon mine, Salt Lake City, Utah, in August 1979, long- 
term, in-mine testing began. A mix of haulage trucks at various surface mine 
sites have been outfitted with the recommended ladder designs to be placed in 
normal operating use for a minimum of 1 year. During this period, the safety, 
maintenance, and acceptability aspects of each design will be evaluated. 



52 



TRAINING MOBILE EQUIPMENT OPERATORS 

by 

Louis Schaffer 1 and Edwin Ayres 2 



ABSTRACT 

Mobile equipment is involved in a large number of the fatal accidents and 
nonfatal injuries in surface mines. Accident and training research suggests 
that one of the principal reasons is the inadequate training provided for many 
mobile equipment operators, especially in terms of their ability to cope with 
unusual and unexpected events. A concept for providing the needed training, 
formulated by Woodward Associates, Inc., and based on personal injury, and 
noninjury, accident phenomena research, is presented and explained. Some of 
the training materials developed to implement the concept are described, 
including an onboard simulator of abnormal conditions. Cost comparisons are 
made between training programs that utilize these materials, customary on-the- 
job training programs, and training programs that might use a high-fidelity, 
all-function simulator as the principal teaching device. 

BACKGROUND 

Anyone who reads information about accidents in surface mining will find 
frequent references to statistics. These always show that some large propor- 
tion of the accidents in surface mines involve mobile equipment. This should 
be no surprise to the reader or, in itself, a cause for concern about equip- 
ment. After all, a very large proportion of the people who work in surface 
mines have jobs that involve them almost exclusively in the operation, ser- 
vicing, or maintenance of mobile equipment. If there are going to be job- 
related accidents, many of the accidents will certainly involve, in one way or 
another, mobile equipment. The data which are important, and the cause of con- 
cern, are those that show the numbers of mobile equipment accidents each year, 
the costs of the accidents, and the numbers and degrees of injuries to workers. 

The best available national mine accident data are those compiled by the 
Mine Safety and Health Administration (MSHA) in Denver. They provide the 
numbers and degrees of injuries to workers. For example, some data from that 
source are given in table 1. These are 1978 data, the most recent full-year 
data available at the time this paper was prepared. Note that there were 
49 fatal accidents and 2,800 nonfatal injury accidents involving the mobile 
equipment types listed. 



IProject manager, Woodward Associates, Inc., San Diego, Calif. 
2 Electrical engineer, Pittsburgh Research Center, Bureau of Mines, 
Pittsburgh, Pa. 



53 



TABLE 1. - Accidents reported to MSHA in 1978 involving 
five mobile equipment types 





Coal 


mines 


Noncoal 


mines 


Total non- 


Mobile equipment 
involved 


Fatal 
accidents 


Nonfatal 

injury 
accidents 


Fatal 
accidents 


Nonfatal 

injury 
accidents 


fatal injury 
accidents, 
all mines 


Off-highway haulers. 
On-highway haulers . . 
Front-end loaders... 


5 
4 
6 
6 
1 


248 
216 
289 
377 
125 


7 
8 
12 

2 


366 
418 
491 
176 
94 


626 
646 
796 
559 




222 




20 


1,255 


29 


1,545 


2,849 



The numbers of accidents in U.S. surface mines that do not produce inju- 
ries to persons are not known. Most mines do not keep accurate records of 
accidents defined as "unplanned events which interrupt the work of the worker- 
machine unit," or, more generally, as "losses" or "avoidable costs." Those 
mines attempting to keep such records commonly include as recordable accidents 
only those having direct material and repair costs equal to or greater than 
some arbitrarily chosen amount, usually between $100 and $500. In short, the 
cost of the majority of noninjury accidents are "hidden" in maintenance or 
other accounts. However, it is possible to make some reasonable estimates 
from the information available from a few mines in the United States and 
Canada and the consensus judgment of several mining company officials with 
long experience in surface mine operations. The estimate developed by Wood- 
ward Associates, Inc., based on these sources, is that there were at least 
22,500 noninjury accidents in 1978 involving the five equipment types listed 
in table 1. That is, there were, for every fatal accident, approximately 
57 nonfatal injury accidents and nearly 460 noninjury accidents (including 
those that actually produced an injury not requiring medical attention and not 
reported to MSHA) . 

Using the same sources of information, it has been estimated that the 
cost of all "noninjury" accidents is at least five times, and perhaps as much 
as 15 times, the cost of all injury accidents, even though the latter often 
include as cost components major medical expenses and much lost time. 



A lengthy study of all of the available information on both injury and 
noninjury accidents produced several useful conclusions. One of these, shared 
by others who have done similar work in other industries and in automobile 
accident research, is astonishment that there are not many more fatalities and 
nonfatal injuries each year than actually occur. A great many accidents that 
produced severe and expensive damage to equipment did no damage at all to the 
operators, although analyses of accident details, without prior knowledge of 
the end result, suggest strongly that the probability of personal injury was 
very high indeed. Additional conclusions from the study parallel those of 
accident research in other areas. For example, Appleby, Bintz, and Keen of 



54 



the Automobile Club of Southern California reported in SAE Paper 770115 3 that 
"education of vehicle owners who possess only limited skill or knowledge, can 
eliminate some accident-causing vehicle defects." Change the words "vehicle 
owners" to "equipment operators" and you have one of the conclusions reached 
by the Woodward Associates staff, a conclusion affirmed by the Bureau of Mines, 
based on other research. 

In SAE Paper 770116 11 prepared by McDole of the Highway Safety Research 
Institute, reporting on a commercial vehicle study initiated by the Bureau of 
Motor Carrier Safety, there are these words: "The most important single recom- 
mendation resulting from the study was that vehicles should receive a thorough 
pre-trip inspection." Change the words "pre-trip" to "pre-shift" and you have 
another of the conclusions reached by the Bureau of Mines and by the Woodward 
Associates staff. Similarly, the other principal conclusions from the study 
have parallels in accident research from industries that use mobile equipment. 
There is a need for better understanding by operators of their roles in their 
companies, including how their performance affects costs and the safety of 
fellow workers. There is a need for thorough, objective job performance stan- 
dards and proficiency tests. There is a need for instruction, demonstration, 
and practice in safe equipment operation procedures under abnormal conditions, 
including those related to operator physical condition impairment, unusual 
weather, and equipment component and system failures. 

TECHNOLOGY 

In order to apply accident research conclusions in a "systems approach" 
to the development of training programs for mobile equipment operators, a 
total training concept was formulated. The final version of this concept can 
be outlined in terms of six elements, as shown in table 2. Although the con- 
cept was developed with surface mining in mind, it is applicable also to 
mobile equipment operator training in other industries. 

TABLE 2. - Outline of 6-element training concept 
Element Training activity 

1 Function orientation. 

2 Personal protection. 

3 Preshift inspection. 

4 Normal operations . 

5 Abnormal operations . 

6 Proficiency demonstration. 

3 Appleby, M. R. , L. J. Bintz, and P. E. Keen, Jr. Incidents Caused by Vehicle 
Defects — Analysis of Their Characteristics. Paper 770115 pres. at SAE 
Internat. Automotive Eng. Cong, and Exposition, Detroit, Mich., Feb. 28- 
Mar. 4, 1977. 

^McDole, T. L. Inspection, Defect Detection, and Accident Causation in Com- 
mercial Vehicles. Paper 770116 pres. at SAE Internat. Automotive Eng. 
Cong, and Exposition, Detroit, Mich., Feb. 28-Mar. 4, 1977. 



55 



The first element, Function Orientation , has the training objectives of 
thoroughly and accurately informing the trainee about the work of the worker- 
machine unit of which he or she is to be a part in the production sequence of 
the mine; of familiarizing the trainee with company production and safety 
rules and procedures and the reasons for their existence; and of making clear 
the performance expectations of the job. Included are such facts as the pur- 
chase cost of the equipment; the cost of its daily operation and maintenance; 
and how the operator's skill and care can affect the daily costs related to 
his or her equipment and to others in the production line. This training ele- 
ment is also an important opportunity to assure the trainee of the employer's 
concern for worker safety and health on the job. 

The second element, Personal Protection , has the objectives of explaining 
to the trainee how he, or she, should prepare for work each shift and how the 
operator should inspect the protection devices installed on the equipment to 
be operated. Topics covered include proper clothing and protection for the 
head, eyes, hearing, feet, hands, and lungs. The trainee is also made 
acquainted with the design limits of rollover protection and falling object 
protection installed on the equipment he, or she, is to operate, the impor- 
tance of inspection, and proper use of the seat safety belt and other personal 
protection items on the equipment such as noise reduction and fire suppression 
devices. 

The third element, Preshift Inspection , instructs the trainee in a check- 
list procedure to assure that the equipment is in proper condition for safe, 
efficient work before the shift is begun. Included among the topics covered 
are tires and wheels, lights, fluid supply levels, fluid line condition, 
engine compartment condition, fire extinguishers, windows, mirrors, backup 
alarm, gages and warning lights, engine operation, brakes, steering, retarders, 
and bucket, bed, or blade operations. 

Elements four and five are Normal Operations and Abnormal Operations , but 
for instruction purposes these two are presented together in sections related 
to specific work activities. For example, for off-highway haulers there might 
be two sections: Haul Road and Yard Operations , and Loading and Dumping . The 
material for normal operations is, for the most part, that adapted from oper- 
ator manuals developed by the mobile equipment manufacturers. It is augmented 
by material from mining companies that have developed operations procedures 
for lowest cost per unit of product; from accident research reports of the 
Bureau of Mines and others; and from study reports on other facets of equip- 
ment operation. The material for much of the abnormal operations training is 
more difficult to acquire. The manuals provided by equipment manufacturers 
provide some material, but usually this is limited to emergency systems 
installed on the equipment. Instructional information of very high reliabil- 
ity can, however, be obtained from manufacturer's field representatives and 
fleet training people. It is also available from accident analyses that were 
sufficiently thorough, and thoughtful, to identify the actions that could have 
prevented the accident or might have reduced the damage and injury severity 
which it produced. A key point is that a given "abnormal condition" usually 
occurs very infrequently. An operator may work many years without ever having 
experienced it, particularly if it is of the component failure or physical 



56 



condition impairment type. It is necessary to catalog the conditions, develop 
the "countermeasures," explain and demonstrate both to the trainee, and pro- 
vide training time in which to practice the countermeasures under simulated 
abnormal conditions. 

The sixth element is Proficiency Demonstration . It is a thorough test of 
operating knowledge and skill. It covers all of the principal points in ele- 
ments two through five. There is no written test. Knowledge is tested by 
verbal responses; skills by demonstration in actual working conditions, includ- 
ing simulated abnormal conditions. It is administered by a mining company 
instructor or supervisor according to a standard procedure and graded in terms 
of a performance standard. 

IN-MINE TESTING 

The Bureau of Mines is sponsoring research, development, and field eval- 
uation of training systems based on the six-element concept. One such program 
is for off-highway haulers; the other is for front-end loaders. Field evalu- 
ations of the hauler system are presently being conducted at a coal mine in 
Kentucky, using a Terex 33-11C hauler, 5 and at a copper mine in Arizona, using 
a Unit Rig Mark 36 hauler. A "system" includes classroom training aids, all 
in a synchronized slide-tape format, instructor's manuals, and trainee work- 
books in a programed instruction style. A system also includes, as one of the 
most important training aids, a device to simulate, in the equipment to which 
it is connected, certain abnormal operating conditions of the equipment. The 
device was developed by Woodward Associates and is called "OBSAC," an acronym 
for "Gn-Board Simulator of Abnormal Conditions." 

A development prototype OBSAC console is shown in figure 1. This model 
is packaged in a briefcase-type container. It connects electrically to mobile 
equipment in which has been installed an OBSAC adapter kit. When so connected, 
it enables the instructor to control the readings of certain of the operator's 
gages, actuate most visual and audible alarms, degrade brake performance, 
degrade steering, and kill the engine. The gages in this OBSAC model are 
water temperature, oil pressure, voltmeter, transmission/converter oil temper- 
ature, transmission/clutch oil pressure, starting air pressure, and brake air 
pressure. There is a digital timing device in the console which enables the 
instructor to determine how long it takes the trainee to observe an abnormal 
indication and to take the proper action. Most of the training is done using 
the OBSAC in the actual equipment and environment in which the operator trainee 
will work. The OBSAC is also used to administer the proficiency demonstration. 
Classroom instruction is about one-quarter of the total planned training time. 
The six slide-tape training aids run less than 20 minutes each. They are 
intended for use in a classroom training session of approximately 45 minutes 
in which the majority of the time is devoted to demonstration and discussion 
of the training points. 

Figure 2 shows the OBSAC in use in a highway-rated tractor during the ini- 
tial development tests at a driver training school in San Diego. Figure 3 shows 

5 Reference to specific trade names is made for identification only and does 
not imply endorsement by the Bureau of Mines. 



57 




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58 




59 




60 



the way in which the OBSAC console is constructed. It uses simple, standard, 
easily available components so that any necessary field repairs may be made 
quickly and at low cost. 

CONCLUSION 

In addition to evaluating the training effectiveness of systems based on 
the six-element concept described here, field tests have provided some needed 
comparative cost data. These tests have made it possible to compare the costs 
of present conventional training of mobile equipment operators with the costs 
of training using a six-element, OBSAC-supported system. Early in the 
research programs sponsored by the Bureau of Mines, several kinds of cost 
analyses were done. Comparisons were made among present conventional training, 
the Woodward Associates' system, and a system also based on the six-element 
concept, but employing as a principal training resource a technically sophisti- 
cated, high-fidelity, full— function, hauler simulator. A 40-hour, primarily 
on-the-job training (OJT) , program was used to estimate median costs of pres- 
ent conventional training. The program was typical of those observed by 
Woodward Associates in many mines. A 39-hour program which included 12 hours 
of instruction and practice in a hypothetical hauler simulator was used to 
estimate costs related to such a system. Simulator construction, maintenance, 
and operating costs were estimated from data obtained from other industries, 
and the armed services, in which simulators are used extensively. 

A summary of the results of these cost analyses is in table 3. Direct 
training cost includes the wages of the trainee, instructor, and simulator 
technicians; cost of operating the equipment (a hauler was used for these 
analyses) and a simulator during training; and training material (including 
OBSAC and full-function simulator) costs apportioned over expected useful life. 
The lower direct cost in the six-element OBSAC system is due largely to the 
increased efficiency of imparting essential information through the use of 
classroom training aids and the OBSAC. The information in table 3 is, in one 
respect, biased in favor of the "six-element with all-function simulator" 
system because travel costs from mine to simulator were not included in the 
"fire-mine cooperative" and "15-mine sponsored training school" cases. (A 
full- function simulator is expensive. In order to keep hourly training costs 
low, it is necessary to assure maximum simulator use. This could be done only 
by having several mines use a single simulator.) Even with "central location," 
some mines would incur significant travel costs for their trainees. 



ffi 



61 



TABLE 3. - Expected costs for alternative hauler training systems 





Training system alternatives 


Alternative 


Median mine 


WAI OB SAC 


Simulator 
supported 


mine settings 


Annual 
mine 
cost 


Cost 

per 

trainee 


Annual 
mine 
cost 


Cost 

per 

trainee 


Annual 
mine 
cost 


Cost 

per 

trainee 




$88,704 
NA 

NA 


$4,928 
NA 

NA 


$65,562 
63,882 

NA 


$3,642 
3,549 

NA 


$319,942 
121,142 

88,009 


$17,774 
6,730 

4,889 


Five-mine cooperative 

15-mine sponsored training 



NA Not available. 

Table 3 obviously does not reflect the value of the training given; that 
is, the degree of operator proficiency achieved. Operator proficiency achieve- 
ment for conventional OJT and for the "six-element with OBSAC" training is 
being tested during the field evaluation in the current Bureau of Mines pro- 
gram. It will not be possible to test proficiency achieved by the "six- 
element with all-function simulator" system, of course, because there is no 
such system in existence. 



•frU.S. GOVERNMENT PRINTING OFFICE: 1980-603-102/53 



INT.-BU.OF MINES, PGH..P A. 24791 






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